I have a VBS script which will modify this all in one go.
(Offered with no warranty etc. I suggest you try it on a test OU first!)
To use it do the following;
Const ADS_PROPERTY_APPEND = 2
Const strOU = "LDAP://OU=Year 11,OU=Students,OU=MON,OU=Establishments,DC=montgomery,DC=internal"
Const strGroup1 = "CN=Teaching Staff E-Mail,OU=Network Operational Groups,OU=Groups,OU=Not On RM,OU=Establishments,DC=montgomery,DC=internal"
Set objOU = GetObject(strOU)
objOU.Filter = Array("user")
For Each objUser In objOU
objUser.PutEx ADS_PROPERTY_APPEND, "dLMemSubmitPerms", _
1. Create a group that you WANT to be able to e-mail students, in this case we called it Teaching Staff E-mail, because we want teachers to be able to e-mail students, but no one else.
2. Program the LDAP string of the container with the users in you want to apply this setting to. You might need to us LDAP browser from softerra to get the correct string, unless you're good at writing them yourself.
3. Run the script. This will add the group teaching staff e-mail into the delivery restrictions for every account in the specified OU so that the students can only receive mail from the members of that group.
EDIT: Note, this method also stops them receiving mail from outside the organisation as well. We don't allow this at the moment, so this method works for us! I think there's probably an addition to the script that can change the radial button too, so you can do it the other way round - 'receive from everyone except'